It’s all about “shore hardness” of various rubbers Stud. What you no doubt are experiencing is…chatter or rolling of the rubber. One sure shot way to avoid it is with using a friction reducer like glide(not sure i should have mentioned that one) as not a real favorite around here:D or try supply’s “Slick” it will help on those problems mentioned.
Basically soft rubber rolls more on hot glass where as hard rubber tends to conform better to hotter glass with less chatter & roll.
I recommend Pulex hard rubber;) Also cut your rubber tight to the channel ends (about a 16th of an inch) help on fish tailing & hang outs.
Just so you know… does not make a hard rubber no one does for those.However i have LFI rubber i get locally (alittle harder of a rubber) if you want i can send you a stick or 2 to try? PM me if interested!